7 - Southern Plains Rivers

Abstract

The Arkansas and the Red—two large, separate river basins—drain the southern Great Plains region of the US south of the Kansas River and north of the Texas–Gulf coastal drainages. Rivers of the region flow through the Southern Plains, Central Prairie, Ozark Highlands, Ouachita Highlands, and Mississippi Embayment “freshwater ecoregions.” The rivers of the region fall into two different groups based on their upland versus lowland characteristics. The group including the Arkansas, Canadian, Red, Washita, and Cimarron rivers represents typical large to medium-size low-gradient prairie main stems with wide, shallow, braided, unstable sand-bed channels, often carrying heavy loads of large wood snags washed in by floods. Late-summer drying of streams in the region is a function of both evapotranspiration and lowered rainfall. Extreme rainfall events result in annual or more frequent bankfull spates and streambed scouring in many of the smaller tributaries to the main rivers. Clearing and snagging rivers for boat passage, contamination by salt water from oil production, and interbasin water transfers have altered the rivers over the years.